In the use of a rotatable shaft, it is desirable to controllably prevent rotation of the shaft and free the shaft for rotation. This permits the shaft to be locked into a position when not in use and also permits rotation of the shaft during use.
Commonly, a rotatable shaft is associated with a motor used to drive attachments on a work vehicle. For example, a motor is mounted in relationship with a backhoe implement to provide swing control of the implement. The motor and shaft are used to position the implement at a convenient working location by swinging the implement about an axis to the desired location.
When not in use, particularly during movement of the work vehicle from jobsite to jobsite, the backhoe implement is customarily moved to a certain position relative to the vehicle. It is desirable to securely maintain this position and prevent the implement from swinging freely in response to forces on the implement and shaft incurred during movement of the work vehicle. For example, the circuit pressure in a hydraulic motor positions the implement during use. When the implement is not in use, leakage can occur in the hydraulic system and permit rotation of the shaft. This situation is increased by forces on the implement tending to turn the shaft against the circuit pressure. This can result in undesirable movement of the implement, interference with the activities of the work vehicle, and a waste of time and labor in repositioning the implement.
Heretofore, a rack and pinion mechanism has been commonly used to control the implement. Maintaining the implement in a locked position has been accomplished by placing safety pins through corresponding openings in respective brackets on the work vehicle and implement. The use of a rotary motor and its associated shaft to control the backhoe implement provides further opportunity to securely and more conveniently lock the implement in position.
Therefore, it is desirable to provide means for controllably preventing rotation of the shaft and freeing the shaft for rotation. This locks the shaft and associated attachments in a particular position when not in use and permits rotation of the shaft during use, respectively.